This application relates generally to gas turbine engines and, more particularly, to methods and apparatus for maintaining gas turbine engine rotor assembly tip clearances.
Gas turbine engines typically include an engine casing that extends circumferentially around a compressor and a turbine including a rotor assembly. The rotor assembly includes at least one row of rotating blades that extend radially outward from a blade root to a blade tip. A circumferential tip clearance is defined between the rotating blade tips and the engine casing.
During engine operation, heat generated by the engine may cause thermal expansion of the rotor assemblies, and render the tip clearance non-uniform circumferentially. As a result, inadvertent rubbing between the rotor blade tips and the engine casing may occur. Continued rubbing between the rotor blade tips and engine casing may lead to premature failure of the rotor blade.
To facilitate optimizing engine performance and to minimize inadvertent rubbing between the rotor blade tips and the engine casing, at least some known engines include a clearance control system. The clearance control system supplies cooling air to the engine casing to promote thermal contraction of the engine casing to facilitate mining inadvertent blade tip rubbing. Because the engine casing should be thermally cooled circumferentially, the clearance control systems include a plurality of complex duct work coupled circumferentially around the engine. However, because the engine thermally contracts and expands during operation, the clearance control system also includes a plurality of sliding joints including seals, and support brackets. Over time, continued exposure to vibrational stresses induced during engine operation, may lead to premature failure of the sliding joints and seals, and lead to an eventual failure of the clearance control system.
In an exemplary embodiment, a gas turbine engine includes an active clearance control system that facilitates extending a useful life of a rotor assembly in a cost effective and reliable manner. The engine includes at least one rotor assembly encased within an engine casing extending circumferentially around the rotor assembly, such that a tip clearance is defined between the rotor assembly and the engine casing. The clearance control system includes a plurality of panels that couple together and extend circumferentially around the engine. Each clearance control system panel includes a circumferential feed duct formed integrally with the panel. Adjacent circumferential feed ducts are coupled in flow communication with flexible connection ducts.
During operation, cooling air is supplied to the clearance control system. The cooling air is then distributed circumferentially around the engine casing. As a result of the cooling air being introduced, the engine casing thermally contracts, thus facilitating maintaining the tip clearance and preventing inadvertent blade tip rubbing against the engine casing, and optimizing engine performance. As a result, the clearance control system facilitates extending a useful life of the rotor assembly in a cost effective and reliable manner.